In a water treatment field, water is classified into a high quality water, a middle quality water and a low quality water. The high quality water presents water usable for drinking or washing, the middle quality water represents water once used and treated for reuse, and the low quality water represents polluted water after use.
The present invention is directed to a composition for decreasing the hardness of water which makes it possible to change raw water having a high hardness to be used for high quality water to drinkable water with an appropriate hardness.
Diverse methods such as a physical treatment, a chemical treatment and a biological treatment are used to decrease the hardness of raw water, and a purification agent is mainly used to help such treatments.
A tap water purification plant has a big scale of facilities in order to decrease the hardness of raw water. The tap water purification plant comprises a flocculating pond for flocculating micro suspension substances, a sedimentation pond for settling the flocculated substance, and a filtering pond for filtering the settled substance via a filtering function. The water purification plant is equipped with a large scale of facilities which are capable of continuously producing a lot of high quality water for 24 hours.
In Korea, multiple water treatment agents are designated. There are seven kinds of flocculation agents such as poly aluminum chloride, aluminum sulfate, etc., and there are five kinds of sterilization disinfection agents such as liquid chlorine, etc., and there are seven kinds of other agents such as active carbon, zeolite, illite, etc., and there is one kinds of rust inhibitor. Twenty kinds of agents are totally designated. The flocculation agent serves to flocculate micro particles suspending and floating in water, and colloid particles to bigger sizes, and settle and separate the same. The illite has an adsorption performance and is generally used as a turbid substance removing agent.
The raw water for tap water which uses natural water as a raw ware contains a lot of mineral components such as Mg, Ca, Fe, etc. The water containing lots of calcium salt and magnesium salt is called hard water, and the water containing less calcium salt and magnesium salt is called soft water. The magnesium and calcium ions in water are from sulfate, hydrogen carbonate, and hydrochloride.
What exists as hydrogen carbonate is needed to boiled and settled, thus being softened, which is called temporal hard water. Since what exists as sulfate is not settled even though it is boiled, it is called permanent hard water. The permanent hard water might be softened when it is treated with ion exchange resins.
The value obtained by changing the number of mg of Mg and Ca contained in 1 l of water into the amount of CaCO3 is called hardness, and the water with higher than 200 hardness is called hard water, and the water with less than 100 is called soft water.
When the hardness of water is higher, it tastes bitters, and when drinking such water, it tastes hard. It is known that the easiness of drinking water is largely affected by the hardness of water, so the hardness is a key factor in evaluating the quality of drinkable water.
Various countries have standards on the allowable hardness on drinkable water. The recommended standard by WHO is less than 500, and in Korean, it is less than 300.
“Tasty water study club” under the health and welfare ministry of Japan suggests, as the conditions of water, nine items of the hardness of 10˜100 mg/l, and isolation oxygen of 3˜30 mg/l, and the presence of SiO2.
The hardness of water is in proportion to the contents of calcium and magnesium ions which are bivalent positive ions in water, and silicic acid serves to make water tasty. As components which worsen the tastes of water, sulfuric acid ions, hydrochloric acid ions and magnesium ions are known as worsening the tastes of water.
The calcium ions and magnesium ions in raw water are mainly from CaSO4 or MgSO4, CaCl2 or MgCl2 and CaHCO3 or MgHCO3.
The hardness of raw water is different from its origin. The hardness of raw water is generally in a range of 80˜500. An appropriate range of hardness for drinkable water is 60˜100. In particular, the raw water produced from a limestone area exceeds the hardness of 500.
The Korean patent registration publication number 10-0330255 disclose a composition of inorganic flocculation agent for water treatment which is prepared by plastic-forming and grinding the mixture of barley stone power, coal fly ash, desulfurized gypsum and zeolite.
The above composition is used for a flocculation of micro floating substances. Since the composition contains harmful components to human such as desulfurized gypsum and coal fly ash, it is not good as a drinkable water treatment agent.
The Korean patent registration publication number 10-0484561 discloses a composition of water treatment for deodorization and heavy metals which is made by forming zeolite, loess, illite and titanium dioxide in the form of granule. The above composition is however not proper as a water treatment agent for decreasing the hardness of raw water.
There is provided a method which removes calcium and magnesium components from hard water by treating the hard water with an ion exchange resin. When the hard water is treated with an ion exchange resin, and the Ca and Mg ions are exchanged with Na ion, most of hard components might be removed from raw water.
When hard water components are all removed from raw water, the mineral components good for human are also removed, so water taste is worsened and becomes like distilled water, which is not proper as a drinkable water. In this case, it is needed to add mineral components for using such water as drinkable water.
A human body requires diverse mineral components. When such mineral components lack, diseases might take place even though only a small amount lacks. Small amount of essential minerals are contained in foods and drinkable water and are supplied to human bodies.
Calcium and magnesium are kinds of essential minerals, and calcium serves to form bone and teeth and helps coagulate blood. When calcium lacks, osteoporosis and coagulation delay problems occur. Magnesium is known to produce adenosine triphosphate which is a key metabolism substance to human. When the hardness of raw water is too high, it tastes bitters, so it does not good for drinkable water. When the hardness of raw water is too low, water tastes hard, and the supply of mineral components useful to human bodies stops, so it is needed to maintain a proper level of hardness for drinkable water. When natural water with a high hardness is supposed to be changed to soft water for the use as drinkable water, it is needed to maintain an appropriate level of hardness for the use as drinkable water, with calcium and magnesium not exceeding the hardness 100. An appropriate water purification, if any, meeting the above standards will be usefully applied in water purification field.